October 28, 2007

Overweight and obesity in young Greek men

Obes Rev. 2007 Oct 24; [Epub ahead of print]

Prevalence of overweight and obesity in young Greek men.

Papadimitriou A, Fytanidis G, Papadimitriou DT, Priftis KN, Nicolaidou P, Fretzayas A.

We determined the prevalence of overweight and obesity in young Greek men in 2006 and examined variations related to their place of residence and educational level. Body height and weight were measured in 2568 conscripts of the Greek army, aged 19-26 years. The calculated body mass index (BMI, kg m(-2)) was correlated to their socio-demographic characteristics, i.e. level of education and place of residence (urban or rural). Overweight and obesity were defined according to the World Health Organization classification. Mean BMI (standard deviation) of the conscripts was 24.7 (4.2). The prevalence of overweight (30 > BMI >/= 25 kg m(-2)) was 28.5% and correlated positively with a higher educational level, whereas the prevalence of obesity (BMI >/= 30 kg m(-2)) was 10.4% and correlated positively with a lower educational level. Our data were compared with those of similar studies performed in the years 1969: BMI 23.8 (1.4) (P < 0.0001) and 1990: BMI 23.8 (2.9) (P < 0.0001), showing a positive secular trend for BMI in Greek conscripts in the last 16 years. In conclusion, we documented an alarmingly high prevalence of overweight and obesity among young Greek men.


Long Live the 28th October 1940

How humans became warlike altruists

Via Yann, I am alerted to a new Science report on the evolution of parochial altruism. The authors describe how hypothetical genes for parochialism (P) and altruism (A) could have co-evolved. Parochial altruists (PA) risk death in combat with other groups. How could the PA combination evolve? 

The authors suggest that PA fighters do risk death, but in conflicts between groups, it is the groups with more PAs that have a higher chance of winning. Thus, while parochial altruists are selected against (because they risk their lives for their group), they are also selected for (because they kill off more members of less-PA groups in violent conflicts). Moreover, the losing side's numbers are replenished by conquerors' genes (thus becoming more PA).

The authors contend that archeologically-derived estimates of group warfare are consistent with their scenario for the evolution parochial altruism. One would think that other, more recent, historical examples could also be used, e.g., between city-state warfare in classical Greece. 

The paper's innovation is that a seemingly "irrational" behavior from selfish genes' point of view could nonetheless evolve. The genes that cause their bearers to die in patriotic battles may die, but their competing alleles on the losing side may suffer more.

Science 26 October 2007:
Vol. 318. no. 5850, pp. 636 - 640
DOI: 10.1126/science.1144237

The Coevolution of Parochial Altruism and War

Jung-Kyoo Choi1 and Samuel Bowles2*

Altruism—benefiting fellow group members at a cost to oneself—and parochialism—hostility toward individuals not of one's own ethnic, racial, or other group—are common human behaviors. The intersection of the two—which we term "parochial altruism"—is puzzling from an evolutionary perspective because altruistic or parochial behavior reduces one's payoffs by comparison to what one would gain by eschewing these behaviors. But parochial altruism could have evolved if parochialism promoted intergroup hostilities and the combination of altruism and parochialism contributed to success in these conflicts. Our game-theoretic analysis and agent-based simulations show that under conditions likely to have been experienced by late Pleistocene and early Holocene humans, neither parochialism nor altruism would have been viable singly, but by promoting group conflict, they could have evolved jointly.

October 20, 2007

Domestication of barley

Genetics. 2007 Oct 18; [Epub ahead of print]

Molecular phylogeography of domesticated barley traces expansion of agriculture in the Old World.

Saisho D, Purugganan M.

Okayama University.

Barley (Hordeum vulgare ssp. vulgare) was first cultivated 10,500 years ago in the Fertile Crescent and is one of the founder crops of Eurasian agriculture. Phylogeographic analysis of five nuclear loci and morphological assessment of two traits in >250 domesticated barley accessions reveals that landraces found in South and East Asia are genetically distinct from those in Europe and North Africa. A Bayesian population structure assessment method indicates that barley accessions are subdivided into 6 clusters, and that barley landraces from 10 different geographical regions of Eurasia and North Africa show distinct patterns of distribution across these clusters. Using haplotype frequency data, it appears that the Europe/North Africa landraces are most similar to the Near East population (FST = 0.15) as well as wild barley (FST = 0.11) and are strongly differentiated from all other Asian populations (FST = 0.34 to 0.74). A neighbor-joining analysis using these FST estimates also supports a division between Europe, North African and Near East barley types from more easterly Asian accessions. There is also differentiation in the presence of a naked caryopsis and spikelet row number between eastern and western barley accessions. The data support the differential migration of barley from two domestication events that led to the origin of barley - one in the Fertile Crescent and another further east, possibly at the eastern edge of the Iranian Plateau - with European and North African barley largely originating from the former while much of Asian barley arising from the latter. This suggests that cultural diffusion or independent innovation are responsible for the expansion of agriculture to areas of South and East Asia during the Neolithic Revolution.


On the James Watson Black IQ controversy

There are two issues regarding the recent controversy started by James Watson's comments about the intelligence of Africans.
The scientist, who won the Nobel prize for his part in discovering the structure of DNA, was quoted in an interview in The Sunday Times saying he was “inherently gloomy about the prospect of Africa” because “all our social policies are based on the fact that their intelligence is the same as ours - whereas all the testing says not really.”
The first issue is that Watson's statements, whether one agrees with them or not should not be punished, and represent a valid stance to the problem of population differences in intelligence. Of course institutions (such as the Cold Spring Harbor lab) have the right to choose who works for them, but they also have the responsibility to foster free speech.

One would be sympathetic to CSH's condemnation of Watson if it was done on scientific grounds. For example, a scientist denying the fact of evolution could not reasonably expect to have no reprecussions in his career. Institutions are expected to make sure they don't promote bad science, which is not necessarily unorthodox science (which should be encouraged), but rather unargued or anti-empirical science.

However, CSH's stance has been motivated by political or social considerations. How could it be otherwise, since the identification of intelligence-fostering genes differentiating populations has not come about yet. The prudent stance is to be agnostic about this issue, until such genes are discovered, or their continued non-discovery makes one doubtful of their existence.

The second issue is that Watson's factual comments are entirely accurate! Sub-Saharan Africans do indeed have lower intelligence than people in western societies. That is an observable fact (fact F). What is not certain is whether or not this fact is due to inherent genetic deficiencies (position A) or due to environmental or socio-cultural problems (position B). Social policies should take into account F while the scientists figure out whether A or B explains F.

As an analogy, a cook has to take into account that his knife is blunt before he figures out whether it is blunt because it was made poorly or from repeated use.

According to Watson:
A priori, there is no firm reason to anticipate that the intellectual abilities of people geographically separated during their evolution should prove to have evolved identically. Our wanting to reserve equal powers of reason as some universal heritage of mankind will not be enough to make it so.
Once again, Watson's comments are reasonable. Notably they do not identify which populations may have inherent (evolutionary) differences in intelligence, nor do they attempt to quantify the importance of such differences. They simply state the -a priori sensible- stance of a scientist that a phenomenon (e.g., the evolution of cognitive ability) would not have proceeded in the same way under different circumstances.

UPDATE: A post-controversy article by James Watson in the Independent. Excerpt:
We do not yet adequately understand the way in which the different environments in the world have selected over time the genes which determine our capacity to do different things. The overwhelming desire of society today is to assume that equal powers of reason are a universal heritage of humanity. It may well be. But simply wanting this to be the case is not enough. This is not science.

October 18, 2007

Limitations of genetic ancestry testing

From the EurekAlert release about an upcoming Science article:
Some of the tests’ limitations identified by Bolnick and her co-authors include:
  • Most tests trace only a few of your ancestors and a small portion of your DNA,
  • Tests are unlikely to identify all of the groups or locations around the world where a test-taker’s relatives are found,
  • Tests may report false negatives or false positives,
  • Limited sample databases mean test results are subject to misinterpretation,
  • There is no clear connection between DNA and racial/ethnic identity,
  • Tests cannot determine exactly where ancestors lived or what ethnic identity they held.

Neanderthals had same version of FOXP2 "language gene" as modern humans

Via National Geographic:
A team of European researchers tested Neandertal bones recovered from a Spanish cave for a certain gene, called FOXP2, that has been dubbed "the speech and language gene."

It's the only gene known so far that plays a key role in language. When mutated, the gene primarily affects language without affecting other abilities.

The new study suggests that Neandertals (often spelled Neanderthals) had the same version of this gene that modern humans share—a different version than is found in chimpanzees and other apes.

"From the point of this gene, there is no reason to think that Neandertals did not have language as we do," said the study's lead author, Johannes Krause of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany.

"Of course many genes are involved in language, so we can't say from this result alone that Neandertals spoke just as modern humans do," Krause added.

Genome-wide detection of positive selection

Nature 449, 913-918 (18 October 2007) | doi:10.1038/nature06250; Received 8 August 2007; Accepted 13 September 2007

Genome-wide detection and characterization of positive selection in human populations

Pardis C. Sabeti et al.

With the advent of dense maps of human genetic variation, it is now possible to detect positive natural selection across the human genome. Here we report an analysis of over 3 million polymorphisms from the International HapMap Project Phase 2 (HapMap2)1. We used 'long-range haplotype' methods, which were developed to identify alleles segregating in a population that have undergone recent selection2, and we also developed new methods that are based on cross-population comparisons to discover alleles that have swept to near-fixation within a population. The analysis reveals more than 300 strong candidate regions. Focusing on the strongest 22 regions, we develop a heuristic for scrutinizing these regions to identify candidate targets of selection. In a complementary analysis, we identify 26 non-synonymous, coding, single nucleotide polymorphisms showing regional evidence of positive selection. Examination of these candidates highlights three cases in which two genes in a common biological process have apparently undergone positive selection in the same population:LARGE and DMD, both related to infection by the Lassa virus3, in West Africa;SLC24A5 and SLC45A2, both involved in skin pigmentation4, 5, in Europe; and EDAR and EDA2R, both involved in development of hair follicles6, in Asia.


October 14, 2007

Conservation of frequently used words in Indo-European languages

I wonder what implications -if any- this finding has on attempts to date the PIE language before the dispersal of its speakers. After all, PIE is constructed based on words found in several (at least two) daughter languages, and thus will tend to use words that are conserved more (since they have survived in more than one language). The implication of this article is that conserved words are replaced at a slower rate. Hence, it is important to take into account the rates of evolution of different terms when trying to figure out how long ago two languages shared a common ancestor.

Nature 449, 717-720 (11 October 2007) | doi:10.1038/nature06176; Received 30 April 2007; Accepted 17 August 2007

Frequency of word-use predicts rates of lexical evolution throughout Indo-European history

Mark Pagel et al.

Greek speakers say "ουρα", Germans "schwanz" and the French "queue" to describe what English speakers call a 'tail', but all of these languages use a related form of 'two' to describe the number after one. Among more than 100 Indo-European languages and dialects, the words for some meanings (such as 'tail') evolve rapidly, being expressed across languages by dozens of unrelated words, while others evolve much more slowly—such as the number 'two', for which all Indo-European language speakers use the same related word-form1. No general linguistic mechanism has been advanced to explain this striking variation in rates of lexical replacement among meanings. Here we use four large and divergent language corpora (English2, Spanish3, Russian4 and Greek5) and a comparative database of 200 fundamental vocabulary meanings in 87 Indo-European languages6 to show that the frequency with which these words are used in modern language predicts their rate of replacement over thousands of years of Indo-European language evolution. Across all 200 meanings, frequently used words evolve at slower rates and infrequently used words evolve more rapidly. This relationship holds separately and identically across parts of speech for each of the four language corpora, and accounts for approximately 50% of the variation in historical rates of lexical replacement. We propose that the frequency with which specific words are used in everyday language exerts a general and law-like influence on their rates of evolution. Our findings are consistent with social models of word change that emphasize the role of selection, and suggest that owing to the ways that humans use language, some words will evolve slowly and others rapidly across all languages.


October 10, 2007

Y chromosomes from the Gulf of Oman

European Journal of Human Genetics advance online publication 10 October 2007; doi: 10.1038/sj.ejhg.5201934

Y-chromosome diversity characterizes the Gulf of Oman

Alicia M Cadenas


Arabia has served as a strategic crossroads for human disseminations, providing a natural connection between the distant populations of China and India in the east to the western civilizations along the Mediterranean. To explore this region's critical role in the migratory episodes leaving Africa to Eurasia and back, high-resolution Y-chromosome analysis of males from the United Arab Emirates (164), Qatar (72) and Yemen (62) was performed. The role of the Levant in the Neolithic dispersal of the E3b1-M35 sublineages is supported by the data, and the distribution and STR-based analyses of J1-M267 representatives points to their spread from the north, most likely during the Neolithic. With the exception of Yemen, southern Arabia, South Iran and South Pakistan display high diversity in their Y-haplogroup substructure possibly a result of gene flow along the coastal crescent-shaped corridor of the Gulf of Oman facilitating human dispersals. Elevated rates of consanguinity may have had an impact in Yemen and Qatar, which experience significant heterozygote deficiencies at various hypervariable autosomal STR loci.


October 04, 2007

TEDtalk by Zeresenay Alemseged

An interesting talk (video) by a paleoanthropologist working in Ethiopia:
About this Talk

Paleoanthropologist Zeresenay Alemseged is looking for the roots of humanity in Ethiopia's badlands. Here he talks about what he has found -- including the oldest skeleton yet discovered of a hominid child -- and how Africa holds the clues to what makes us human.

About Zeresenay Alemseged

Zeresenay "Zeray" Alemseged digs in the Ethiopian desert, looking for the earliest signs of humanity. His most exciting find: the 3.3-million-year-old bones of Selam, a 3-year-old hominid child, from the species Australopithecus afarensis.
Lots more TEDtalks if you love science.

October 01, 2007

Neanderthals of the East

A new paper from Svante Paabo's team that shows that Neanderthals may have lived further to the east that can be assumed based on paleoanthropological evidence. Roughly speaking, to identify some remains as Neanderthals, anthropologists have to detect features belonging to the "constellation of features" typical of that species. However, when the material is limited in quantity, one cannot do this: most of the Neanderthal-identifying features are missing! Obviously, this is not a problem with DNA methods, since DNA can be extracted from small bone and tooth fragments.

Nature advance online publication 30 September 2007 | doi:10.1038/nature06193

Neanderthals in central Asia and Siberia

Johannes Krause et al.

Morphological traits typical of Neanderthals began to appear in European hominids at least 400,000 years ago1 and about 150,000 years ago2 in western Asia. After their initial appearance, such traits increased in frequency and the extent to which they are expressed until they disappeared shortly after 30,000 years ago. However, because most fossil hominid remains are fragmentary, it can be difficult or impossible to determine unambiguously whether a fossil is of Neanderthal origin. This limits the ability to determine when and where Neanderthals lived. To determine how far to the east Neanderthals ranged, we determined mitochondrial DNA (mtDNA) sequences from hominid remains found in Uzbekistan and in the Altai region of southern Siberia. Here we show that the DNA sequences from these fossils fall within the European Neanderthal mtDNA variation. Thus, the geographic range of Neanderthals is likely to have extended at least 2,000 km further to the east than commonly assumed.